Field of the Invention
The present invention relates to a method for manufacturing a component, such as a spherical lens, particularly used in optical devices, and also relates to a polishing apparatus.
Description of the Related Art
A spherical lens, which is an optical element used in optical devices, is polished by supplying abrasive slurry to a polishing tool having a spherical operating surface similar to the surface of the spherical lens, causing the polishing tool to apply pressure to a workpiece, and also causing the polishing tool to rotate the workpiece and make the workpiece perform an oscillating movement. The oscillating movement is performed, with the center of curvature of the surface of the workpiece coinciding with the center of curvature of the surface of the polishing tool. This oscillating movement transfers the surface shape of the polishing tool to the optical element, so that a desired shape of the optical element can be obtained.
As a polishing apparatus that polishes a spherical lens, Japanese Patent Publication No. 6-65460 describes a polishing apparatus that performs polishing by applying pressure toward the spherical center of a polishing plate to make the polishing plate oscillate. Japanese Patent No. 4347374 describes a polishing apparatus that includes linear motion shafts provided with linear guides. By controlling each of the linear motion shafts, this polishing apparatus performs an oscillating movement in which the center of curvature of the surface of the workpiece coincides with the center of curvature of the surface of the polishing tool.
Each of the polishing apparatuses described in Japanese Patent Publication No. 6-65460 and Japanese Patent No. 4347374 is configured to make the polishing plate oscillate and is distant from the spherical center. Therefore, since the range of oscillation is large, it is necessary to improve apparatus stiffness and movement accuracy to achieve a high-accuracy oscillating movement, and this increases the apparatus cost. Lowering the cost of the polishing apparatus leads to an increase in spherical center error due to a decrease in apparatus stiffness and movement accuracy. This causes a nonuniform distribution of contact pressure between the surface of the workpiece and the surface of the polishing tool, and makes it difficult to achieve desired shape accuracy.